JP2013000708A - Powder coating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a powder coating device which coats every part of a coating object with a sufficiently thick coating film, even if the coating object has pits and projections or narrow gaps, and is excellent in the powder coating material use efficiency.SOLUTION: A powder coating material is accommodated in a powder container 21 into which fluid air 23 is fed from a porous material 22 on a bottom surface, and a powder coating material fluid layer 21a and a powder coating material atomization layer 21b are formed, by the fluid air 23, on a lower part and an upper part in the powder container 21, respectively, and a feeding nozzle 25 which feeds the powder coating material, which is frictionally electrified by a frictional electrifying gun 24, is installed on the upper face of the fluid layer 21a in the powder container. Then, the frictionally electrified powder coating material, which is fed from the feeding nozzle 25, is mixed with the powder coating material in the atomization layer 21b, and this powdery mixture is brought into contact with a coating object 20 to electrostatically adhere to the object.

Description

  The present invention relates to a powder coating apparatus that can adhere a frictionally charged powder coating material with high efficiency without spraying the object to be coated.

  Powder coating does not contain organic solvents, and overspray powder that has not adhered to the object to be coated can be collected and reused, so it has been adopted in many products in recent years as an environmentally friendly coating.

  It started with road materials such as guardrails and fences, and is widely used in products used at home such as refrigerators and air conditioner outdoor units. Recently, it is often used to paint school chairs, desks, and hospital partitions.

  Powder coating is also used for coating automotive parts, which is one of the key industries in Japan, and operates automotive parts in addition to wipers, missions, drive shafts, brake pads, aluminum wheels, license plates. It is also used for insulation coating of small motors. In automobiles, there are 100 to 200 small motors per car, in the cockpit, around the engine, etc. in addition to power windows, car mirrors, door locks, headlights, steering locks, power seats, seat belts, electric parking brakes and transfers. in use. In the future, it is also considered to be used in drive motors for hybrid cars and electric cars.

  In general, powder coating is performed by using a corona gun or a frictional charging gun and spraying a powder coating on an object to be coated.

  In the case of a corona gun, an electric field is generated between the corona electrode at the tip of the gun and the object to be coated, and the powder paint discharged from the gun is attached to the object by corona discharge.

  In addition, the friction charging gun includes a non-conductive resin tube, for example, in the gun, and the powder paint is passed through the non-conductive resin tube to cause friction between the non-conductive resin and the powder paint. Thus, the charged powder coating discharged from the gun tip adheres to the object to be coated by electrostatic force.

  Naturally, in both of the above-described methods, as shown in FIG. 18, the powder coating 3 is discharged from the coating gun 1 toward the workpiece 2 by forced air such as compressor air, for example. Overspray powder that does not adhere to the surface is generated. For this reason, the painting operation is performed in the painting booth 4, and overspray powder that does not adhere to the workpiece 2 is sucked and collected from the suction port 5 provided in the painting booth 4. The overspray powder collected by suction is reused after passing through a screening device.

  However, the paint particle size distribution of the recovered powder is greatly different from that of the new powder, and there are many paints that are difficult to adhere to the article 2 to be coated. For this reason, a problem remains with respect to the object 2 to be coated, and a large number of painting guns are required to paint.

  Since the frictional charging gun does not have an electric field like the corona gun, even if it is a concavo-convex object to be coated, it is preferable that the powder coating enters the inner surface.

  For this reason, it can be used also for the coating which forms an insulating film in the rotor of a motor in which many teeth are arranged in the radial direction at narrow intervals.

  In order to coat the rotor 2a with the frictional charging gun 6, as shown in FIG. 19, a screw conveying device 7 for moving the rotor 2a is provided in the painting booth 4, and the inside of the painting booth 4 is moved by the screw conveying device 7. It is possible by spraying powder paint from the discharge nozzle 8 where the triboelectric gun 6 branches against the passing rotor 2a.

  However, since the frictional charging gun 6 frictionally charges the powder coating by passing it through the charging tube with strong conveying air, the air pressure of the conveying air contained in the discharged powder coating is high. Since the powder paint adhering to the object to be coated is blown off, it is suitable for thin film coating but not for thick film coating.

  When the insulation coating of the rotor 2a of the motor is applied by a coating apparatus using the frictional charging gun 6 as shown in FIG. 19, a thin film type coating of 100 μm or less can be applied, but a thick film type of 200 μm or more is possible. There was a problem that painting was not possible.

  On the other hand, there is an electrostatic fluidized immersion device as a powder coating device that does not depend on spraying from a coating gun.

  As shown in FIG. 20, the electrostatic fluid immersion apparatus is provided with a corona electrode 11 to which a high voltage is applied by a high voltage generator 10 in a powder container 9 containing a powder coating material, and the corona electrode 11 generates the corona electrode 11. This is an apparatus for attaching a powder coating to the article 2 passing through the powder container 9 by an electric field.

  The powder container 9 of the electrostatic fluidized immersion apparatus has a bottom portion partitioned by a porous material 12 such as a porous resin or a campus cloth. A fluidized air 13 is supplied to the lower portion of the porous material 12 to The powder coating is fluidized as if it were a liquid.

  The corona electrode 11 is installed on the porous material 12 or inside or on the lower surface of the porous material 12 in order to prevent the electrode from being contaminated, and forms an electric field between the corona electrode 11 and the object to be coated 2. I am doing so.

  In this case, in the powder container 9, the part of the fluidized bed 14 in which the powder coating is flowing as if it were a liquid, and the part of the atomized layer 15 in the state of being atomized (clouded) above the fluidized bed 14. And are formed. And even if the article 2 is immersed in the fluidized bed 14 where the powder paint is flowing like a liquid, the powder paint does not adhere to the article 2 but is in the vicinity of the porous material 12. The powder paint that is atomized (clouded) in the portion of the atomized layer 15 by the electric field from the corona electrode 11 adheres to the object to be coated 2.

  An example of such a coating method is also disclosed in Non-Patent Document 1. In Non-Patent Document 1, for example, about 2/3 of an object to be coated is immersed in a fluidized powder paint, and 1/3 is coated in an atomized layer (cloud), and the object to be coated is gradually raised. Thus, the remaining portion is sufficiently coated by passing through the atomized layer (cloud).

  Thus, even if the article 2 is immersed in the fluidized bed 14, the powder paint 2 does not adhere to the article 2 because the fluidized bed 14 flows like a liquid. This is considered to be because the air in the fluidized bed 14 is dilute and an electric field cannot be generated.

  In the electrostatic fluidized immersion apparatus in which the corona electrode 11 is installed in the powder container 9, since the coating is performed only with the atomized layer 15 above the fluidized bed 14, the size of the object to be coated 2 is limited. The first reason is that the height of the portion of the atomized layer 15 is low, and generally it can be applied only to the object to be coated 2 of about 100 mm. The second reason is that when the distance between the corona electrode 11 and the object to be coated 2 is increased, an electric field is not formed. Therefore, the distance between the object to be coated 2 and the corona electrode 11 is generally about 250 mm. Yes.

  Therefore, in the electrostatic fluid immersion apparatus in which the corona electrode 11 is installed in the powder container 9, the object to be coated 2 is limited to a small one such as a micromotor as shown in FIG. For this reason, generally, the mist formed on the fluidized bed 14 without immersing the article 2 in the fluidized bed 14 in which the powder coating is flowing like a liquid. The present condition is that the coating of adhering the powder coating material of the atomizing layer 15 to the article 2 is performed by passing the forming layer 15.

  Moreover, in the electrostatic fluid immersion apparatus in which the corona electrode 11 is installed in the powder container 9, the material of the powder container 9 is limited to an insulating material. That is, if the material of the powder container 9 is conductive, for example, metal, all the electrons discharged from the corona electrode 11 are discharged to the (metal) material of the nearby powder container 9, and the object to be coated An electric field cannot be formed between the two and the powder coating material cannot be adhered to the article 2 to be coated.

  Further, when the distance from the porous material 12 on which the corona electrode 11 is installed to the object to be coated 2 is increased, that is, when the distance from the corona electrode 11 is increased, even if the powder paint is floating, the distance to the object to be coated 2 is increased. The electric field is weakened and the powder coating is difficult to adhere.

  In addition, there is a fluid immersion method that does not use static electricity as another painting method, and it is often used for painting bicycle bicycles, net fences, and the like.

  In this method, as shown in FIG. 21, a preheating furnace 17, a fluidized tank 18 for storing powder coating material in a fluidized state, and a baking / drying furnace 19 are installed along a line 16 for conveying an object 2 to be preheated. After preheating the object to be coated 2 in the furnace 17 to a temperature of about 270 ° C., the object to be coated 2 is moved above the fluid tank 18 that can be moved up and down, and the fluid tank 18 is raised to enter the fluid tank 18. This is a method in which the powder paint is melted and adhered to the surface of the article to be coated 2 by immersing the article to be coated 2. Thereafter, the fluidized tank 18 is lowered to take out the object 2 to be coated, supplied to the baking and drying furnace 19, and reheated at a temperature of about 200 ° C. to apply the paint adhering to the surface of the object 2 to be coated. Smooth the skin. Thereafter, unloading is performed from the line 16.

  In this preheating dipping method, the film thickness is as large as 400 μm or more. Also, the powder coating that can be used is limited to thermoplastic resins such as vinyl chloride and polyethylene, and epoxy and polyester powder coatings cannot generally be used. In addition, the powder coating tends to sag due to the immersion after preheating.

Published by Cortec Co., Ltd. “Electrostatic powder coating” by J. F. Hughes, pp. 60-65

  As described above, the conventional electrostatic coating method, in which powder coating is applied to an object to be coated, is not made of a thin wire such as an object to be coated with unevenness or a net fence. If there is a place where the powder paint is hard to hit, the part is likely to be poorly painted.

  In addition, since many of the discharged paints become overspray powder, there is a problem that the coating efficiency is poor.

  On the other hand, the coating method using an electrostatic fluidized immersion device in which a corona electrode is installed in a powder container containing a powder coating has a longer residence time of the powder coating around the object to be coated than gun coating. Since the body paint does not always stay there, it is difficult to enter the uneven portions that are particularly difficult to paint. Further, it is difficult for the electric field of the corona electrode to reach the concave portion of the object to be coated, and it is difficult to keep the powder coating around the concave portion.

  The fluidized dip coating method in which the object to be coated is preheated is efficient in using the powder paint, but has a problem that the object to be coated needs to be preheated and becomes a thick film. There is also a problem that the powder coating that can be used is limited.

  Therefore, according to the present invention, it is possible to apply a coating film having a sufficient film thickness to every corner of the concavo-convex part even if the object has a concavo-convex part that is difficult for the powder paint to enter by spray coating of the powder paint. In addition, an object is to provide a powder coating apparatus in which the use efficiency of the powder coating is good.

  In order to solve the above-mentioned problems, a powder coating apparatus according to the present invention contains a powder coating material in a powder container to which flowing air is supplied from a porous material on the bottom surface, A powder coating fluidized layer is formed in the lower part and an atomized layer of the powder paint is formed in the upper part, and the powder paint that has been frictionally charged by the frictional charging gun is discharged on the upper surface of the fluidized layer in the powder container. A nozzle is installed, and the frictionally charged powder paint discharged from this discharge nozzle is mixed with the powder paint of the atomized layer. The body is attached.

  The mixed powder and the object to be coated may be contacted inside the powder container, or a mixed powder outflow passage is formed in the upper portion of the powder container, and the mixed powder is formed in the outflow passage. And the object to be coated may be brought into contact with each other.

  The discharge nozzle is oriented horizontally, upward, or downward with respect to the upper surface of the fluidized bed.

  It is preferable that the discharge nozzles of the frictional charging gun are branched into a large number and installed in the powder container.

  The tip of the discharge nozzle may be formed by a bendable angle adjusting nozzle.

  The powder container may be a circular tank.

  The powder container can be formed of a non-conductive resin or a conductive material such as a metal or a conductive resin.

  As described above, the powder coating apparatus according to the present invention mixes the atomized powder paint and the frictionally charged powder paint so that the atomized powder paint is also charged. It becomes a state, and even if it is an uneven | corrugated shaped to-be-coated object, a powder coating adheres to every corner.

  The powder paint discharged from the frictional charging gun is mixed with the atomized powder paint, so that the discharge air is weakened. Adhere with sufficient thickness.

1 is a schematic longitudinal sectional front view showing a first embodiment of the present invention. (A) is a front view of the to-be-painted object of a 1st Example, (b) is a side view. 1 is a schematic plan view of a first embodiment of the present invention. It is a fragmentary sectional view which shows the example of installation of the discharge nozzle inserted in a powder container. It is a fragmentary sectional view which shows the example of installation of the discharge nozzle inserted in a powder container. It is a fragmentary sectional view which shows the example of installation of the discharge nozzle inserted in a powder container. (A) and (b) are sectional drawings which show the example of a change of a discharge nozzle. It is a schematic longitudinal front view which shows the coating test apparatus of this invention. It is a side view which shows the film thickness measurement point of the to-be-painted object of the coating experiment using the coating apparatus of 1st Example of this invention. It is a schematic plan view which shows the coating process of 1st Example of this invention. (A) (b) (c) is a fragmentary sectional view which shows the relationship between the discharge nozzle inserted in a powder container, and a friction charging gun. It is a schematic longitudinal front view which shows the 2nd Example of this invention. FIG. 13 is a partial cross-sectional view of FIG. 12. It is a perspective view which shows the to-be-painted object of 2nd Example of this invention. (A) is an end elevation which shows the film thickness measurement point of the to-be-painted object of the coating experiment using the coating apparatus of the 2nd Example of this invention, (b) is a front view. It is a schematic longitudinal cross-sectional front view which shows the 3rd Example of this invention. It is a side view which shows the film thickness measurement point of the to-be-painted object of the coating experiment using the coating apparatus of 3rd Example of this invention. It is the schematic of the conventional electrostatic coating apparatus. It is the schematic of the electrostatic coating apparatus which uses the conventional friction charging gun. It is the schematic of the conventional electrostatic fluid immersion apparatus. It is the schematic of the conventional preheating immersion apparatus.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
FIG. 1 shows a first embodiment of the present invention in which the object to be coated 20 is a rotor 20a of a motor.

  As shown in FIGS. 2A and 2B, the rotor 20a has a large number of teeth 20b arranged in the radial direction at a narrow interval, and an insulating film is provided on the outer surface of the teeth 20b. In the first embodiment, this insulating coating is formed by powder coating, and a green epoxy powder coating is used as the powder coating.

  As shown in FIG. 1, the powder coating apparatus of the first embodiment has a powder container 21 to which flowing air 23 is supplied via a porous material 22 on the bottom surface. A powder coating material is accommodated in the powder container 21. The powder coating material in the powder container 21 becomes a fluidized bed 21a that flows in a liquid state by the fluidized air 23 from the bottom surface, and the atomized layer 21b that floats in the atomized state (cloud state) at the top. Become.

  Discharge nozzles 25 branched into a large number of friction charging guns 24 are inserted into the upper surface of the fluidized bed 21 a in the powder container 21, and the powder paint frictionally charged from the discharge nozzles 25 enters the powder container 21. Supplied and mixed with the powder coating of the atomized layer 21b.

  The material of the powder container 21 is stainless steel in the above embodiment, but may be formed of a conductive resin. The powder container 21 is grounded, and the total charge of the powder container 21 can be reduced by forming it with a conductive material.

  Further, even if the powder container 21 is made of an insulating material, for example, a tank made of vinyl chloride, as in the case of the conventional electrostatic fluid immersion apparatus, there is no difference in the amount of attachment and the attachment.

  A suction hood 26 is installed on the upper surface of the powder container 21, and the frictionally charged powder paint mixed with the powder paint of the atomizing layer 21 b is drawn out from the opening 27 on the upper surface of the powder container 21. .

  The powder paint collected by the suction hood 26 is sent to the paint tank 29 via the dust collector 28 and is reused.

  On the upper surface of the powder container 21, a screw conveying device 30 is installed along the opening 27. The screw conveying device 30 rotates the rotor 20 a as the object to be coated 20 from one end of the opening 27 to the other. It is transferred at a predetermined speed toward the end.

  From the opening 27 on the upper surface of the powder container 21, the powder coating material of the atomized layer 21b and the frictionally charged powder coating material are drawn out in a mixed state, and the rotor 20a, which is the object 20 to be coated, is drawn through this drawing channel. Passes through the narrow teeth 20b of the rotor 20a, and the powder coating material of the atomized layer 21b and the frictionally charged powder coating material enter in a mixed state.

  The core shaft 20 c of the rotor 20 a is masked by the chuck 31 of the screw conveying device 30. The screw 32 of the screw conveying device 30 is formed of a conductive material, and the rotor 20a that is the article to be coated 20 is grounded (grounded) via the screw 32.

  The powder coating material of the atomizing layer 21b and the frictionally charged powder coating material adhere to the outer surface of the rotor 20a.

  The film thickness of the adhering powder coating can be adjusted by changing the speed of the screw conveying device 30 that conveys the rotor 20a. That is, if the transfer speed of the rotor 20a is slowed down, the adhesion time of the powder coating becomes longer, so that the film thickness increases accordingly. On the contrary, if the transfer speed is increased, the adhesion time of the powder coating is shortened, so that the film thickness is reduced.

  The discharge nozzles 25 of the triboelectric gun 24 are branched into a large number and, as shown in FIG. 3, are inserted into the rectangular powder container 21 in two rows so as to face each other along the transfer direction of the rotor 20a. It is rare.

  The directions of the discharge nozzles 25 are arranged in combination with the upper surface of the fluidized bed 21a in the horizontal, diagonally downward, and diagonally upward directions.

  When the direction of the discharge nozzle 25 is directed horizontally with respect to the upper surface of the fluidized bed 21a as shown in FIG. 4 or obliquely upward as shown in FIG. 5, the powder is atomized from the upper surface of the fluidized bed 21a. The body paint is unlikely to rise, and conversely, as shown in FIG. 6, when it is directed obliquely downward, it tends to rise from the upper surface of the fluidized bed 21a in the form of a mist. Therefore, the concentration of the powder coating material contained in the atomized layer 21b can be adjusted by appropriately changing the direction of the discharge nozzle 25.

  As shown in FIGS. 7A and 7B, the discharge nozzle 25 may have a structure in which the direction can be freely changed.

  The concentration of the powder coating material contained in the atomized layer 21 b can be adjusted by the amount of the carrier air discharged from the discharge nozzle 25 and the amount of the flowing air 23 in addition to the direction of the discharge nozzle 25.

  An overflow slit 33 is provided on the side surface of the powder container 21 in order to make the height of the fluid tank 21 a constant, and the overflowed powder paint is collected in the paint tank 29. Overspray powder sucked from the suction hood 26 is collected in the paint tank 29 via a dust collector 28. The powder coating material collected in the coating material tank 29 is supplied to the frictional charging gun 24 by the injector 35 via the quantitative supply device 34.

  The paint tank 29 is replenished with powder paint from the new powder tank.

  An exhaust duct 37 having a damper 36 is provided above the powder container 21 in order to adjust the concentration of the powder coating material of the atomized layer 21 b, and the exhaust duct 37 is connected to the suction hood 26.

  By the way, the powder coating material of the atomizing layer 21b and the powder coating material that is frictionally charged adhere to the object to be coated 20 because the powder coating material of the atomizing layer 21b and the powder material that is frictionally charged are mixed. Thus, it is considered that pseudo-charging was performed on the powder coating material of the atomized layer 21b.

  In order to confirm this experimentally, as shown in FIG. 8, a flat test piece 38 is installed on the upper surface of the opening 27 of the powder container 21, and the powder in the fluidized bed 21 a in the powder container 21. The color of the paint is white, the color of the powder paint discharged from the discharge nozzle 25 of the friction charging gun 24 into the powder container 21 is green, and the powder paint from the discharge nozzle 25 of the friction charging gun 24 is made green. When the supply is performed, that is, when the frictional charging gun 24 is turned on, when the supply of the powder paint from the discharge nozzle 25 of the frictional charging gun 24 is stopped, that is, when the frictional charging gun 24 is turned off. An experiment was conducted on how the powder coating adhered to the test piece 38.

  The experiment was performed by setting the discharge amount from the frictional charging gun 24 to 20 g / min and the carrier air to 0.1 MPa with respect to the desired film thickness of 80 μm.

When the frictional charging gun 24 is OFF, the white powder paint in the powder container 21 hardly adheres to the test piece 38. Next, when the frictional charging gun 24 was turned on, the white and green powder paints were adhered to the test piece 38 in a mixed state. The adhering white and green powder coatings adhere to the inside of the coating film in a mixed state, and the white powder coating is mixed with the green powder coating charged with frictional charging. This is considered to be pseudo-charged and attached to the test piece 38 together with the green powder paint.
The experimental results are summarized in Table 1.

  Next, using the coating apparatus of the embodiment shown in FIG. 1, the discharge rate of the triboelectric gun 24 is 30 g / min, the transfer air is 0.1 MPa, and the transfer speed of the screw transfer apparatus 30 is 1.0 m / min. Table 2 shows the results of a motor rotor coating experiment conducted at 6 m / min.

  As a result, in the coating with a conveyance speed of 0.6 m / min, the film thickness was thicker than that with a conveyance speed of 1.0 m / min, and a desired film thickness of 200 μm was obtained.

  Table 2 shows the average value of film thickness (μm) of 10 lots in 4 lots, and the film thickness measurement points are points a to p in FIG.

  As shown in FIG. 10, the rotor 20a coated as described above is used to remove excess powder on the outer periphery with a roller brush and an air knife on a surplus powder removing tank 39, and then a high-frequency heating device and a hot air circulating furnace. In the baking oven 40 equipped with this, the coating film is melt-cured and then unloaded.

  In the embodiment of FIG. 1, the discharge nozzle 25 of the frictional charging gun 24 is arranged in the atomization layer 21b above the fluidized bed 21a. However, as shown in FIG. 11A, the discharge nozzle 25 is placed in the fluidized bed 21a. You may arrange. When the discharge nozzle 25 is disposed in the fluidized bed 21a, the powder coating material in the fluidized bed 21a may flow backward from the discharge nozzle 25. Therefore, as shown in FIG. 11B or FIG. 11C, the supply pipe of the discharge nozzle 25 is provided with a portion that bends above the fluidized bed 21a before the discharge nozzle 25 to prevent backflow. Is desirable.

  Next, FIG.12 and FIG.13 has shown the Example of the coating device which uses the slide shaft 20d which is a motor vehicle part as the to-be-coated object 20. FIG.

  As shown in FIG. 14, the slide shaft 20d has, for example, a length of 230 mm, a width of 23 mm, and a cross-sectional shape in cross section.

  The outer surface of the slide shaft 20d is coated to a thickness of 300 μm and then finished to a thickness of 200 to 250 μm by cutting. The painted surface is in the range of A in FIG. As the powder coating material, a nylon-based powder coating material such as that manufactured by Arkema is used.

  When coating the slide shaft 20d, degreasing is performed before coating, primer blasting is performed after shot blasting, and then drying is performed.

  A shaft installation base 41 is provided on the upper surface of the powder container 21, and the powder coating of the atomization layer 21 b mixed with the charged powder paint discharged from the frictional charging gun 24 on the shaft installation base 41. Eight powder flow path pipes 42 for pulling out the powder upward are provided in an annular shape.

When eight slide shafts 20d, which are the objects to be coated 20, are hung on the hangers 43 in the eight powder passage pipes 42 and inserted from above, the inner surfaces of the powder passage pipes 42 and the slide shaft 20d are formed. The powder paint passing through the gap with the outer surface adheres to the outer surface of the slide shaft 20d.
The inner diameter of the powder passage pipe 42 is 10 to 30 mm larger than the outer diameter of the slide shaft 20d.

  The gap between the inner diameter of the powder passage pipe 42 and the slide shaft 20d, which is the object to be coated 20, is appropriately determined according to conditions such as the particle size distribution of the powder coating material and the desired film thickness.

  A concentration adjusting damper 45 that adjusts the powder coating concentration of the atomized layer 21 b in the powder container 21 is installed at the center of the shaft installation table 41.

  A plurality of discharge nozzles 25 branched and extended from the frictional charging gun 24 are uniformly arranged on the side surface of the powder container 21.

  The discharge nozzle 25 is inserted above the upper surface of the fluidized bed 21 a in the powder container 21. The reason why the discharge nozzle 25 is inserted above the upper surface of the fluidized bed 21a in the powder container 21 is that the powder paint rubbed from the discharge nozzle 25 is discharged and then the coating is finished. Since the powder coating material in the fluidized bed 21a drifts like water, the powder coating material in the fluidized bed 21a flows backward from the discharge nozzle 25 toward the frictional charging gun 24, and then the powder in the fluidized bed 21a. There is a possibility that the powder coating material is blocked in the supply pipe between the discharge nozzle 25 and the frictional charging gun 24 due to air escape. In order to eliminate this closed state, the closed state can be prevented by inserting the discharge nozzle 25 above the upper surface of the fluidized bed 21a.

  When the discharge nozzle 25 is inserted into the fluidized bed 21a, as shown in FIGS. 11B and 11C, the supply pipe in front of the discharge nozzle 25 is provided with a bent portion that bends upward from the upper surface of the fluidized bed 21a. By forming, the backflow of the powder coating material to the discharge nozzle 25 and the frictional charging gun 24 is prevented.

  The charged powder paint discharged from the discharge nozzle 25 of the frictional charging gun 24 hits the powder paint flowing in the fluidized bed 21a, is mixed with the fluidized powder paint, and is clouded on the fluidized bed 21a. Create an atmosphere of atomization. The powder coating in the cloud state passes through the gap between the powder passage pipe 41 and the slide shaft 20d.

  In the second embodiment, the slide shaft 20d is fixed. However, the slide shaft 20d may be rotated in the powder passage pipe 42 in order to increase the uniformity.

  The coating in the powder passage pipe 41 may be performed once, but for example, the top and bottom of the slide shaft 20d may be turned over to perform the coating again. The slide shaft 20d is melted and cured in a high-frequency device after painting.

  In the second example, when the discharge from the discharge nozzle 25 was performed at 100 g / min for 55 seconds, the film thickness was as shown in Table 3.

  The measurement points of the film thickness in this coating test are as shown in FIGS. 15 (a) and 15 (b).

  The film thickness (μm) represents the average value of the eight slide shafts 20d.

  In the second embodiment, the powder container 21 has a circular shape, and suction hoods 26 are provided at four locations around the powder passage pipe 41 to collect overspray powder in the paint tank 29 for collection. .

  The point that the slit 33 for overflow is provided in order to supply the frictional charging gun 24 from the paint tank 29 and to keep the height of the fluid tank 21 a at the side surface of the powder container 21 is the first. The same as the embodiment.

  Next, FIG. 16 shows a third embodiment of the present invention in which the slide rail 20e of the shelf plate of the refrigerator is the object to be coated 20.

  In this embodiment, as the powder coating material, a polyester-based material having good sliding properties is used.

  The slide rail 20e is L-shaped as shown in FIG.

  As in the first and second embodiments, the powder container 21 has a fluidized bed 21a and an atomized layer 21b formed therein.

  The powder container 21 is a square type, and a discharge nozzle 25 of a frictional charging gun 24 is inserted into an opposing surface above the fluidized bed 21a.

  The concentration of the powder coating material in the atomized layer 21b tends to become thinner as it goes upward.

  Since the slide rail 20e has a long vertical length, in order to make the film thickness uniform, after dipping the slide rail 20e to be coated 20 into the fluidized bed 21a, the slide rail 20e is raised, The slide rail 20e can pass through the atomized layer 21b sufficiently to form a stable and uniform coating film.

  Seven slide rails 20e are suspended in parallel on the hanger 44, inserted into the powder container 21 from the opening 27 of the powder container 21, and are lifted upward after painting.

  The slide rail 20e is degreased, treated with iron phosphate, washed with water, and drained before drying.

  The slide rail 20e is transported to the upper surface of the powder container 21 by a tact operation while being hung and is dipped on the fluidized bed 21a of the powder container 21.

  Then, the frictional charging gun 24 is operated while being dipped, and the powder coating material of the atomizing layer 21b on the upper surface of the fluidized bed 21a and the powder coating material frictionally charged are mixed.

  Thereafter, when the slide rail 20e is raised and passed through the atomization layer 21b mixed with the frictionally charged powder paint, the powder paint uniformly adheres to the slide rail 20e.

  In the third embodiment, a suction hood 26 is provided above the opening 27 of the powder container 21 and the overspray powder is collected in the paint tank 29 for collection.

  In order to supply the frictional charging gun 24 from the paint tank 29 and to make the height of the fluid tank 21 a constant at the side surface of the powder container 21, an overflow slit 33 is provided. The same as in the second embodiment.

  The slide rail 20e is melted and cured in the high frequency device after painting.

  In the third embodiment, when the coating test was performed with the discharge amount from the discharge nozzle 25 being 120 g / min, the film thickness was as shown in Table 4.

  The film thickness measurement points in this coating test are as shown in FIG. The film thickness (μm) represents the average value of the seven slide rails 20e suspended from one hanger 44. The coating test was performed three times in total.

20 Object 20a Rotor 20b Teeth 20c Core shaft 20d Slide shaft 20e Slide rail 21 Powder container 21a Fluidized layer 21b Atomized layer 22 Porous material 23 Fluidized air 24 Friction charging gun 25 Discharge nozzle 26 Suction hood 27 Opening 28 Dust collector 29 Paint tank 30 Screw conveying device 31 Chuck 32 Screw 33 Slit 34 Fixed amount supply device 35 Injector 36 Damper 37 Exhaust duct 38 Test piece 39 Surplus powder removal tank 40 Baking furnace 41 Shaft installation table 42 Powder passage pipe 43 Hanger 44 Hanger 45 Concentration adjustment damper

Claims (8)

  Powder coating is contained in a powder container to which fluidized air is supplied from the bottom perforated plate, and a fluidized layer of powder coating is formed in the lower part of the powder container and an atomized layer of powder coating is formed in the upper part by the flowing air. A discharge nozzle that discharges the powder coating frictionally charged by the frictional charging gun on the upper surface of the fluidized bed in the powder container, and the frictionally charged powder coating discharged from the discharge nozzle; A powder coating apparatus comprising: mixing a powder coating of an atomized layer, bringing the mixed powder into contact with an object to be coated, and attaching the mixed powder to the object to be coated.   2. The powder coating apparatus according to claim 1, wherein the mixed powder adheres to the object to be coated by bringing the mixed powder into contact with the object to be coated inside the powder container.   A mixed powder outflow passage is formed in an upper portion of the powder container, and the mixed powder and the object to be coated are brought into contact with each other in the outflow passage to adhere the mixed powder to the object to be coated. The powder coating apparatus according to claim 1.   The powder coating apparatus according to claim 1, wherein the discharge nozzle is directed to the upper surface of the fluidized bed.   The powder coating apparatus according to any one of claims 1 to 4, wherein the discharge nozzle of the frictional charging gun is branched into a large number.   6. The powder coating apparatus according to claim 1, wherein a tip of the discharge nozzle is formed by a bendable angle adjusting nozzle.   The powder coating apparatus according to any one of claims 1 to 6, wherein the powder container is a circular tank.   The powder coating apparatus according to any one of claims 1 to 7, wherein the powder container is formed of a non-conductive resin or a conductive material such as a metal or a conductive resin.

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